This invention relates to an exhaust gas purifying device installed in an exhaust gas system of an internal combustion engine for removing dusts, solid particles or the like. The exhaust gas purifying device of the invention is especially useful in an engine such as a motor cycle engine in which the range of exhaust gas flow rates is relatively wide.
If solid particles in the form of spark or engine flames are discharged from an exhaust gas system of an internal combustion engine into the atmosphere, not only is the environment contaminated but, in a place where the combustible or ignitable materials exist, such as a gasoline station, an accidental fire is liable to be caused. This is very dangerous. In view of this matter, the exhaust gas containing the solid particles from the exhaust pipe is limited under some vehicle laws, and an exhaust gas purifying device as well as a muffler is typically used in the exhaust gas system of a vehicle.
A conventional exhaust gas purifying device will now be described. The exhaust gas purifying device comprises a hollow cylindrical member installed in an exhaust gas system and swirl-generating means having a plurality of spiral vanes which are provided on the upstream side of the hollow cylindrical member. In operation, the introducing gas is swirled by the swirl-generating means in the cylindrical member, and solid particles are moved or collected toward an inner wall of the cylindrical member by the centrifugal force, as a result of which floating particles are removed. This manner has been widely used as a so-called centrifugal-force particle removing method.
However, in the above-described method, if the swirling motion or speed is low, the exhaust gas purifying effect is scarcely obtained. Therefore, the conventional exhaust gas purifying device has a disadvantage that the effective exhaust gas purifying effect cannot be obtained in low load conditions of an engine wherein the amount of the exhaust gas is small. In a motorcycle engine having a wide range of exhaust gas amounts, such a disadvantage is remarkable.
A further problem in conventional exhaust gas purification devices is that the capacity for solid particle storage is relatively low in relation to the size of the device. This is particularly troublesome in vehicles such as motorcycles in which it is desirable to maintain vehicle weight and size as low as posslble.